Subterranean barriers, methods, and apparatuses for forming, inspecting, selectively heating, and repairing same

ABSTRACT

A subterranean barrier and method for forming same are disclosed, the barrier including a plurality of casing strings wherein at least one casing string of the plurality of casing strings may be affixed to at least another adjacent casing string of the plurality of casing strings through at least one weld, at least one adhesive joint, or both. A method and system for nondestructively inspecting a subterranean barrier is disclosed. For instance, a radiographic signal may be emitted from within a casing string toward an adjacent casing string and the radiographic signal may be detected from within the adjacent casing string. A method of repairing a barrier including removing at least a portion of a casing string and welding a repair element within the casing string is disclosed. A method of selectively heating at least one casing string forming at least a portion of a subterranean barrier is disclosed.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.10/982,506, filed Nov. 4, 2004, entitled SUBTERRANEAN BARRIERS INCLUDINGAT LEAST ONE WELD, now U.S. Pat. No. 7,160,061, which is acontinuation-in-part of application Ser. No. 10/411,534, filed Apr. 4,2003, now U.S. Pat. No. 6,896,446, entitled ADVANCED CONTAINMENT SYSTEM,which is a divisional of application Ser. No. 09/729,435, filed Dec. 4,2000, now U.S. Pat. No. 6,575,663 B2, entitled ADVANCED CONTAINMENTSYSTEM, the disclosure of each of which is incorporated in its entirety,respectively by reference herein. U.S. application Ser. No. 10/982,506is also a continuation-in-part of application Ser. No. 10/358,633, filedFeb. 4, 2003, now U.S. Pat. No. 6,910,829, entitled IN SITU RETRIEVAL OFCONTAMINANTS OR OTHER SUBSTANCES USING A BARRIER SYSTEM AND LEACHINGSOLUTIONS AND COMPONENTS, PROCESSES AND METHODS RELATING THERETO, thedisclosure of which is incorporated in its entirety by reference herein.

GOVERNMENT RIGHTS

The United States Government has rights in the following inventionpursuant to Contract No. DE-AC07-99ID13727 between the U.S. Departmentof Energy and Bechtel BWXT Idaho, LLC and Contract No.DE-AC07-05-ID14517 between the U.S. Department of Energy and BattelleEnergy Alliance, LLC.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to subterranean barriers for wastemanagement formed by improved methods, apparatuses, and systems.Particularly, the present invention relates generally to methods,apparatus, and systems for joining adjacent casing sections positionedwithin respective subterranean boreholes. For example, the presentinvention relates to methods and apparatus for joining, via at least oneweld, a plurality of casings to one another to form a substantiallycontinuous barrier.

2. State of the Art

Containment, management, and disposal of various types of waste, such aschemical, nuclear, and other potentially harmful types of waste arerecognized, longstanding problems. It is also well recognized thatburied waste may often include heavy metals such as mercury or cadmium,carcinogenic materials such as trichloroethylene, radioactive materials,or other hazardous substances. Such hazardous materials within buriedwaste may be leached (i.e., carried from the waste within a liquid)therefrom, into surrounding soil and into the groundwater. Because wateris used for human consumption and for agriculture, contamination ofgroundwater by leaching is a major concern.

However, the contamination caused by buried waste may not be limitedsolely to groundwater. For instance, contaminated groundwater may becarried into other waterways such as streams, rivers, and lakes, thuspolluting those waterways and leading to poisoning of plant and animallife. In addition, polluted waterways pose a threat to humans as well,particularly in the case of waterways and bodies of water used forrecreational purposes or as sources of drinking or irrigation water.

Also, while many of the problems associated with buried waste arise fromthe effect of leachate on water systems, buried waste may also emit gasphase contaminants that may cause deleterious effects if not containedand managed. For instance, such gas phase contaminants may pollute thesoil and the groundwater, and may build up to unsafe concentrations orpressures, if contained, which could ultimately result in an explosion,or pollution of the atmosphere by venting of the gas.

Accordingly, a variety of methods and devices have been devised toattempt to resolve the problems related to buried waste. These remediesmay be broadly grouped into the categories of remediation andcontainment. Generally, remediation focuses on processes designed tochange the chemical composition of a contaminated material orcontaminant to a more benign chemical composition, while containmentremedies seek to isolate contaminants and contaminated material withinan area or remove them from an area.

Remediation approaches such as biological treatments, thermal processes,and chemical processes may be problematic for a variety of reasons. Inparticular, many remediation techniques may be expensive and potentiallyhazardous. Further, it may be difficult to verify the effectiveness ofmany remediation treatments. Also, determining the proper or optimumremediation technique for a given contamination scenario may be, initself, a complex and time-consuming process.

Containment, barrier, or in situ, approaches may be problematic as well.One known containment approach is simply to dig up and remove thecontaminated soil for treatment or disposal. This approach is expensiveand time-consuming and often accomplishes little more than moving theproblem to another location. Of course, finding an acceptable ultimatedisposal location is another significant impediment to movement of acontaminated region. Other containment approaches involve installingvertical barriers, horizontal barriers, or both types of barriers aroundthe buried waste. In theory, this approach is attractive because it doesnot require digging up or otherwise disturbing the buried waste.

However, conventional containment or barrier systems suffer from avariety of inadequacies including a lack of durability, corrosionresistance, and structural integrity. These inadequacies are a functionof numerous factors associated with the environment in which thecontainment or barrier systems are located including, but not limitedto: exposure to harsh chemicals such as concentrated saline solutions,saturated calcite and gypsum solutions; exposure to extreme thermalgradients; and exposure to stresses induced by shifting in the earthwithin and adjacent the contaminated area. In addition, conventionalbarrier systems may suffer from inadequate ability to monitor or verifythe integrity thereof as well as inadequate reparability thereof if afailure should occur.

Accordingly, recently, containment systems that are designed to contain,collect, or process effluent which would otherwise escape from a zonecontaining waste materials, have been developed. One such containmentsystem is disclosed in U.S. Pat. No. 6,575,663 to Kostelnik, et al.,assigned to the assignee of the present invention, the disclosure ofwhich is incorporated in its entirety by reference herein. Moreparticularly, U.S. Pat. No. 6,575,663 discloses a barrier comprising aseries of adjacent casing strings that are interlocked with one anotherand may be filled with a barrier filling material to form asubstantially continuous wall. Casing strings are disclosed as beingdisposed within the subterranean formation by way of so-called“microtunneling” techniques.

For instance, a barrier is first installed underneath the zone ofinterest. Specifically, a line of individual steel casing sections areplaced by a micro-tunneling device or the like which simultaneouslyexcavates a tunnel and installs connecting casing segments behind themicro-tunneling device as tunneling progresses. The length of thetunnels is determined by the size of the zone of interest to becontained. Preferably, the tunneling device includes a system forensuring accurate placement and orientation of the tunnels and casingsections. As each tunnel is dug and lined with casing sections, asuccessive adjacent tunnel is dug and casing sections situated thereinwhich longitudinally interlock with the casing sections placed in thepreviously excavated tunnel, so as to form a continuous barrier ofpredetermined width.

The casing sections, the joints whereby they interlock adjacent casingsections, or both may be filled with a filler, such as a grout or thelike, for providing an added measure of strength, durability, andimperviousness to the barrier. In a preferred embodiment, two verticalbarrier sections are interlocked with the ends of a horizontal barriersection so that the horizontal barrier and vertical barrierscollectively form a continuous U or channel-shaped containment boundaryextending around the zone of interest.

However, the integrity of such a barrier may, prematurely, fail due torepeated thermal stresses, or movement of the casing strings within thesubterranean formation. For instance, filler within the casing sectionsmay crack, or may otherwise become infirm.

In view of the foregoing problems and shortcomings with existing barrierapparatus, methods, and systems, it may be desirable to provide improvedmethods, apparatus, and systems in relation thereto. Also, it may bedesirable to form barriers for waste management by such improvedmethods, apparatus, and systems.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to barriers for waste management within asubterranean formation. Particularly, a subterranean barrier accordingto the present invention may comprise a plurality of casing stringspositioned within a subterranean formation. Further, each of theplurality of casing strings may be laterally adjacent to at least oneother casing string of the plurality of casing strings and at least onecasing string of the plurality of casing strings may be affixed to atleast another adjacent casing string of the plurality of casing stringsthrough at least one weld. Alternatively, at least one casing string ofthe plurality of casing strings may be affixed to at least anotheradjacent casing string of the plurality of casing strings through atleast one adhesive joint. Optionally, at least one casing string of theplurality of casing strings may be affixed to at least another adjacentcasing string of the plurality of casing strings through both at leastone weld and at least one adhesive joint.

The at least one casing string of the plurality of casing strings andthe at least another adjacent casing string may be directly welded toone another or may be indirectly affixed to one another through at leastone weld. For instance, the at least one casing string of the pluralityof casing strings and the at least another adjacent casing string mayeach be welded to at least one closure element.

In one embodiment, an interlocking structure extending between the atleast one casing string of the plurality of casing strings and the atleast another adjacent casing string of the plurality of casing stringsmay comprise a male interlocking structure and a female interlockingstructure at least partially cooperatively engaged with one another.Further, the at least one weld may be formed between the maleinterlocking structure and the female interlocking structure, directlyor through at least one closure element.

In a method of forming a barrier adjacent a selected region of asubterranean formation according to the present invention, a pluralityof casing strings may be placed within a subterranean formation so thateach of the plurality of casing strings is laterally adjacent to atleast one other casing string of the plurality of casing strings.Additionally, at least two laterally adjacent casing strings of theplurality of casing strings may be affixed to one another by forming atleast one weld.

Of course, at least two laterally adjacent casing strings of theplurality of casing strings may be directly welded to one another or maybe indirectly affixed to one another through at least one weld. Forinstance, the at least two laterally adjacent casing strings of theplurality of casing strings may each be welded to at least one closureelement.

The present invention also relates to a method of selectively heating atleast one casing string forming at least a portion of a barrier within asubterranean formation comprising a plurality of casing strings, whereineach of the plurality of casing strings is laterally adjacent to atleast one other casing string of the plurality of casing strings.Particularly, a heating apparatus may be positioned within a bore of acasing string forming at least a portion of a barrier adjacent aselected region of a subterranean formation and a portion of the casingstring may be selectively heated by operating the heat delivery device.

Another aspect of the present invention relates to a method ofinspecting a barrier within a subterranean formation comprising aplurality of casing strings wherein each of the plurality of casingstrings may be laterally adjacent to at least one other casing string ofthe plurality of casing strings. Particularly, a radiographic signal maybe emitted from within at least one of the plurality of casing stringstoward an adjacent casing string of the plurality of casing strings andthe radiographic signal may be detected from within the adjacent casingstring of the plurality of casing strings.

Also, the present invention relates to a system for inspecting a barrierwithin a subterranean formation comprising a plurality of casingstrings, wherein each of the plurality of casing strings is laterallyadjacent to at least one other casing string of the plurality of casingstrings. Specifically, the system may include a radiographic sourceconfigured for emitting a radiographic signal from within at least oneof the plurality of casing strings toward an adjacent casing string ofthe plurality of casing strings. Further, the system may include aradiographic detector configured for detecting the radiographic signalfrom within the adjacent casing string of the plurality of casingstrings.

Additionally, the present invention relates to a method of repairing abarrier within a subterranean formation comprising a plurality of casingstrings, wherein each of the plurality of casing strings is laterallyadjacent to at least one other casing string of the plurality of casingstrings. For instance, at least a portion of a casing string of theplurality of casing strings may be removed and a repair element may bewelded within the casing string.

In yet a further aspect of the present invention, at least one casingstring of the plurality of casing strings and the at least anotheradjacent casing string may be directly adhesively joined to one anotheror may be indirectly affixed to one another through at least oneadhesive joint. For instance, the at least one casing string of theplurality of casing strings and the at least another adjacent casingstring may each be adhesively joined to at least one closure element.

In one embodiment, an interlocking structure extending between the atleast one casing string of the plurality of casing strings and the atleast another adjacent casing string of the plurality of casing stringsmay comprise a male interlocking structure and a female interlockingstructure at least partially cooperatively engaged with one another.Further, the at least one adhesive joint may be formed between the maleinterlocking structure and the female interlocking structure, directlyor through at least one closure element.

In a method of forming a barrier adjacent a selected region of asubterranean formation according to the present invention, a pluralityof casing strings may be placed within a subterranean formation so thateach of the plurality of casing strings is laterally adjacent to atleast one other casing string of the plurality of casing strings.Additionally, at least two laterally adjacent casing strings of theplurality of casing strings may be affixed to one another by forming atleast one adhesive joint.

Of course, at least two laterally adjacent casing strings of theplurality of casing strings may be directly welded to one another or maybe indirectly affixed to one another through at least one adhesivejoint. For instance, the at least two laterally adjacent casing stringsof the plurality of casing strings may each be adhesive joined to atleast one closure element.

Further, the present invention contemplates that a subterranean barrieradjacent a selected region of a subterranean formation may comprise aplurality of casing strings positioned within a subterranean formation,wherein at least two of the plurality of casing strings are structuredand positioned with respect to one another for forming at least one ofat least one adhesive joint and at least one weld therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming that which is regarded as the present invention,the advantages of the present invention can be more readily ascertainedfrom the following description of the invention when read in conjunctionwith the accompanying drawings in which:

FIG. 1 shows a perspective cut-away view of a subterranean barrier ofthe present invention;

FIG. 2 shows a cross-sectional view of two interlocked, adjacent casingsections that may form a portion of the subterranean barrier shown inFIG. 1;

FIG. 3A shows an enlarged partial cross-sectional view of theinterlocking structure shown in FIG. 2, including a welding apparatusincluding a single welding head positioned within a bore of one of thecasing sections;

FIG. 3B shows a perspective view of a sectioned casing sectioninterlocked with an adjacent casing section, as shown in FIG. 2;

FIG. 3C shows an enlarged partial cross-sectional view of theinterlocking structure shown in FIG. 3A, including welds formed therein;

FIG. 3D shows an enlarged partial cross-sectional view of theinterlocking structure shown in FIG. 2, including a welding apparatusincluding a plurality of welding heads positioned within a bore of oneof the casing sections;

FIG. 4A shows an enlarged partial cross-sectional view of theinterlocking structure shown in FIG. 2, including a NDT apparatuspositioned within a bore of one of the casing sections;

FIG. 4B shows an enlarged partial cross-sectional view of theinterlocking structure shown in FIG. 2, including a NDT apparatusincluding a radiographic source positioned within a bore of one of thecasing sections and a detection device positioned in a bore of the otherof the casing sections;

FIG. 5A shows a partial cross-sectional view of two adjacent,interlocked casing strings which may form a portion of a subterraneanbarrier according to the present invention; and

FIG. 5B shows an enlarged partial cross-sectional view of theinterlocking structure as shown in FIG. 5A, including welds formedtherein;

FIG. 6 shows an enlarged partial cross-sectional view of theinterlocking structure as shown in FIG. 4A, including sealing elementspositioned between the male interlocking structure and the femaleinterlocking structure;

FIG. 7A shows an enlarged partial cross-sectional view of anotherembodiment of an interlocking structure according to the presentinvention including sealing elements;

FIG. 7B shows the enlarged partial cross-sectional view of theinterlocking structure shown in FIG. 7A, including welds formed therein;

FIG. 8A shows an enlarged partial cross-sectional view of anotherembodiment of an interlocking structure according to the presentinvention;

FIG. 8B shows the enlarged partial cross-sectional view of theinterlocking structure shown in FIG. 8A, including welds formed therein;

FIG. 9 shows an enlarged partial cross-sectional view of anotherembodiment of an interlocking structure including a channel feature andfiller material within a recess of the interlocking structure;

FIG. 10 shows a cross-sectional view of three interlocked, adjacentcasing sections that may form a portion of the subterranean barriershown in FIG. 1 during selective heating thereof for repairing of fillermaterial within a recess of an interlocking structure;

FIG. 11A shows an enlarged partial cross-sectional view of theinterlocking structure shown in FIG. 2, including a adhesive affixationapparatus including a single adhesive deposition head positioned withina bore of one of the casing sections; and

FIG. 11B shows an enlarged partial cross-sectional view of theinterlocking structure as shown in FIG. 5A, including adhesive jointsformed therein.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to forming subterranean barriers for wastemanagement by improved methods, apparatuses, and systems, wherein thesubterranean barrier comprises a plurality of adjacent, tubular casingstrings. More particularly, the present invention relates to joining atleast two adjacent tubular casing strings to one another, by way of atleast one weld, to form a barrier containment system.

FIG. 1 shows a perspective cut-away view of a subterranean barrier 140according to the present invention, which may be formed by the methodsof the present invention. Particularly, subterranean barrier 140 maycomprise a plurality of adjacent casing strings 142 including at leastone weld adjoining at least two of the plurality of casing strings 142to one another. Subsurface region 110 may include buried waste 133, asshown in FIG. 1, or another material or concern that renderssubterranean barrier 140 desirable or necessary. Thus, subterraneanbarrier 140 may be formed generally underneath subsurface region 110 andfor substantially containing, treating, monitoring, or otherwiseinteracting therewith.

As shown in FIG. 1, a pipe jacking apparatus 111 and microtunnelingmachine 102 may be employed to form a plurality of adjacent casing-linedtunnels generally surrounding and underneath a subsurface region 110.Particularly, casing strings 142 may comprise a plurality of casingsections 120 affixed to one another and extending longitudinally(lengthwise) in an end-to-end relationship and may be disposed withinsubterranean formation 108, as by tunneling or drilling methods andapparatus as known in the art. Particularly, casing strings 142 maycomprise a plurality of casing sections 120 affixed to one another in anend-to-end relationship, as by threaded surfaces, welding, or both.Further, each of casing strings 142 may be positioned within each oftunnels either substantially contemporaneously as tunneling progresseswith microtunneling machine 102, or subsequent to forming a tunnel, soas to form a lined, tubular structure inside each tunnel.

Thus, microtunneling machine 102 may be employed to form a plurality ofadjacent casing-lined tunnels underneath a subsurface region 110. In oneembodiment, each tunnel may be substantially circular in cross section.However, this invention contemplates that each tunnel may exhibit any ofa wide variety of different cross-sectional shapes (e.g., rectangular,triangular, I-beam shaped, etc.). As shown in FIG. 1, each tunnel beginsin trench 112 and ends in a trench (not shown) on the other side ofsubsurface region 110. Similarly, each casing string 142 may exhibit anyof a wide variety of different cross-sectional shapes (e.g.,substantially circular, substantially rectangular, substantiallytriangular, I-beam shaped, etc.). Also, casing sections 120 may comprisea metal, such as steel (e.g., carbon steel or stainless steel),aluminum, or the like. However, any alternative materials that providesufficient functionality and durability are encompassed within thepresent invention. Alternative exemplary casing materials include, butare not limited to, a polymer, such as PVC, HDPE, polypropylene, orPVDF, vitrified clay, concrete or cement, fiberglass, or other suitablematerials as known in the art.

Further, optionally, the casings strings 142 disposed within theadjacent tunnels may be interlocked to form a subsurface subterraneanbarrier 140. More specifically, as adjacent tunnels may be formed andlined with casing strings 142, each including a plurality of casingsections 120, wherein each casing section 120 of a casing string 142installed within a tunnel may be interlocked with, along a side wallthereof, an adjacent casing section 120 of an adjacent casing string 142disposed within an adjacent tunnel so that a substantially continuoussubterranean barrier 140 may be formed. Accordingly, each of casingsections 120 may be interlocked with at least one other adjacent casingsection 120 through complementary interlocking structures.

More specifically, FIG. 2 shows a partial cross-sectional view of oneexemplary embodiment of two adjacent casing sections 120 that may form aportion of subterranean barrier 140, the two adjacent casing sections120 interlocked with one another by way of interlocking structure 130.Interlocking structure 130, as shown in FIG. 2 includes a maleinterlocking structure 124 and a female interlocking structure 122. Moregenerally, however, each of casing sections 120 may include at least onemale interlocking structure 124, at least one female interlockingstructure 122, or combinations thereof, without limitation. Each casingsection 120, as shown in FIG. 2, comprises a tubular body 126 forming abore 127. For simplicity, bore 127, as used herein, may refer to thebore of a casing section 120 or may refer to the bore of a casing string142 that is formed by a plurality of casing sections 120 affixed to oneanother in an end-to-end relationship. As mentioned above, each ofcasing sections 120 may comprise different, noncircular tubularcross-sectional shapes, as known in the art.

Each female interlocking structure 122 may include guide features 123that form an opening 137 that extends longitudinally along bore 127 oftubular body 126. Thus, opening 137 may extend substantially along theentire length of casing section 120. Optionally, a frangible protectiveelement 144 may be initially disposed across the opening 137 formedbetween the circumferentially adjacent portions of guide features 123.Of course, disposing a male interlocking structure 124 within a femaleinterlocking structure 122, as shown in FIG. 2, may perforate thefrangible protective element 144 associated therewith as the leading endof the male interlocking structure 124 proceeds longitudinally (i.e.,along the length of casing section 120) within the female interlockingstructure 122 of an adjacent casing string 142 (FIG. 1), according tothe drilling or tunneling process for forming casing-lined tunnelsmentioned above.

Generally, according to the present invention, at least two of thecasing strings 142 comprising subterranean barrier 140 may be affixed toone another subsequent to placement within a subterranean formation,through at least one welded joint. As discussed hereinbelow, at leasttwo casing strings 142 may be welded directly to one another or may eachbe welded to a common element or member so as to affix or join the atleast two casing strings 142 to one another. Accordingly, the at leasttwo casing strings 142 may be structured for forming at least one weldtherebetween.

Accordingly, a welding process according to the present invention willbe described with reference to FIGS. 3A-3C. Particularly, FIG. 3A showsa partial side cross-sectional view of two casing sections 120 ofrespective, adjacent, interlocked casing strings 142, as shown in FIG.2, including welding apparatus 210 positioned within bore 127 of onecasing section 120 by positioning legs 212. Positioning legs 212 mayinclude one or more wheels and may be biased by way of a biasing element(not shown) configured for positioning welding apparatus 210 within abore of a substantially tubular structure, such as the (substantiallycircular) bore 127 of casing section 120. Also, welding apparatus 210may be movable along the length of a casing string 142, within a bore127 of one of the plurality of casing sections 120 comprising same. Ofcourse, welding apparatus 210 may be configured for performing weldingprocesses within a bore 127 of each of casing strings 142.

“Weld,” as used herein, means to unite or join two articles by causingat least a portion of the articles to at least partially flow together.Explaining further, welding apparatus 210 may be suited (i.e., sized,configured, and structured) for selectively delivering sufficient heat,energy, materials, solvents, or combinations thereof to a desired regionfor forming a weld between two adjacent casing strings 142. Generally,welding apparatus 210 may be configured for performing any weldingoperation as known in the art, without limitation. For example, and notby way of limitation, welding apparatus may be suited for performing gaswelding, arc welding, gas-shielded arc welding, oxyfuel welding (e.g.,acetylene, oxyacetylene, or oxyhydrogen), laser welding, inductionwelding, electron beam welding, chemical welding (also known as “solventwelding”), ultrasonic welding, resistance welding, or combinationsthereof. Therefore, generally, a weld formed via welding apparatus 210may comprise at least one of a heat-induced weld, a chemical weld, andan ultrasonic weld, or another weld as known in the art, withoutlimitation.

Accordingly, by way of further example, welding apparatus 210 maycomprise a welding apparatus for forming an internal weld within apipeline as disclosed by, for example, any of U.S. Pat. No. 3,424,887 toFehlman, U.S. Pat. No. 5,435,478 to Wood et al., U.S. Pat. No. 5,601,225to Wood et al., U.S. Pat. No. 3,582,599 to Yohn, and U.S. Pat. No.5,593,605 to Jones. Optionally, since both ends of a casing string 142may be accessible, a cable may be affixed to the welding apparatus 210and the welding apparatus may be pulled through a casing string 142.Such a configuration may simplify the design of welding apparatus 210.

Thus, at least one welding head 222 may be affixed to welding apparatus210 and configured for movement within a bore 127 of casing section 120,so as to be selectively positionable for forming a weld upon a desiredportion of an interior of a casing section 120. Thus, welds W, as shownin FIG. 3C, may be formed by a welding apparatus 210 including a singlewelding head 222, as shown in FIG. 3A, configured for forming at leastone weld within casing section 120 of casing string 142. Welding head222 may be at least sufficiently positionable within bore 127 forforming each of welds W as shown in FIG. 3C. Thus, in one contemplatedconfiguration, each of welds W shown in FIG. 3C may be formedsequentially, by positioning welding head 222 proximate a desired regionof the side cross-sectional region of a casing section 120 and operatingwelding head 222 while moving welding head 222 longitudinally within thebore 127 of casing section 120. Of course, welding head 222 may beconfigured in relation to the type of welding technology employed bywelding apparatus 210. For example, if welding apparatus 210 comprises alaser welding apparatus, welding head 222 may comprise a mirror fordirecting a laser beam toward a region desired to be welded.

Thus, as shown in FIG. 3A and described above, a welding apparatus 210may be provided within a bore 127 of a casing section 120 and configuredfor traveling along the longitudinal length of at least one casingstring 142 and for forming a welded joint affixing a casing string 142and at least one adjacent casing string 142 to one another, at leastalong a portion of the respective, adjacent longitudinal lengthsthereof. Of course, considering a subterranean barrier 140 as shown inFIG. 1, each of the plurality of casing strings 142 may be welded alongsubstantially the entire length thereof to each casing string 142adjacent thereto so that the entire subterranean barrier 140 is formedof a plurality of casing strings 142 affixed to one another,respectively, through at least one welded joint.

Also, optionally, it may be preferable to seal or at least partiallyisolate a region of a casing string 142 within which a welding apparatus210 is operating (e.g., wherein a weld is being formed) so as to enhancethe formation of at least one formed therewith. Accordingly, weldingapparatus 210 may include both sealing elements (not shown) as well as agas delivery system (not shown) for performing welding in a suitable,controlled atmosphere within a selected region of bore 127 of casingstring 142. For instance, gas-shielded welding operations may beperformed within an at least partially isolated longitudinal region of acasing string 142 flooded by a selected gas. Therefore, sealing elements(not shown) may be provided for at least partially isolating alongitudinal region of casing string 142 and gas may be communicated ordelivered to the at least partially isolated longitudinal region of thecasing string 142. However, it may be desired that sealing elements donot contact, but only closely mimic or emulate, the interior of casingstring 142 because welding apparatus 210 may preferably move easilywithin casing string 142.

As mentioned above and as shown in FIG. 3A, casing sections 120 formingcasing strings 142 disposed within the adjacent tunnels may beinterlocked, by way of complementarily-shaped interlocking structures,(e.g., male and female) along a side thereof, to form a substantiallycontinuous subsurface subterranean barrier 140. Generally, ampleclearance may be provided between complementarily-shaped interlockingstructures of adjacent casing strings 142 to allow for ease ininstallation, particularly where casing strings 142 may exhibitcurvature along their length. Therefore, generally, gaps or clearancemay exist within interlocking structure 130 formed between adjacent,interlocked casing sections. Particularly, as shown in FIG. 3A, femaleinterlocking structure 122 may comprise an opening 137 formed betweenguide features 123. Further, a distance between guide features 123 mayexceed the size of male interlocking structure 124; therefore, gaps,labeled “g” may be formed longitudinally along the length of casingstrings 142, between the male interlocking structure 124 and each ofguide features 123, respectively.

According to one aspect of the present invention, at least one gapformed between interlocking structures of two adjacent casing stringsmay be substantially or completely closed or sealed by forming at leastone weld. For instance, in one embodiment, as shown in FIG. 3A, closureelements 220 may be placed adjacent guide features 123 and maleinterlocking structure 124, respectively. Closure elements 220 may beconfigured for substantially or completely closing, collectively andupon welding of each closure element 220 to a respective guide feature123 and a respective portion of male interlocking structure 124, gaps gformed between the female interlocking structure 122 and the maleinterlocking structure 124. Put another way, since clearance betweenmale interlocking structure 124 and guide features 123 may be desirablefor assembling adjacent casing strings 142 to one another, a closureelement 220 may be configured for matingly engaging both a guide feature123 and a male interlocking structure 124 so as to substantially orcompletely close the clearance or gap upon welding of the closureelement 220 to both the male interlocking structure 124 and a guidefeature 123. Welding apparatus 210 may be configured for positioningclosure elements 220 in a desired position for welding, as shown in FIG.3A. In one embodiment, closure elements 220 may comprise a so-called“bar stock,” comprising, for instance, steel, aluminum, a polymer, oranother material compatible for welding to male interlocking structure124 and guide feature 123, and may exhibit a cross-sectional shape thatis suitable for matingly engaging, if properly positioned, both a guidefeature 123 and the male interlocking structure 124. Accordingly,closure elements 220 may comprise a polymer such as PVC, HDPE,polypropylene, PVDF, or the like.

Thus, in one embodiment, closure elements 220 may each comprise asubstantially continuous elongated body having a sufficient length toextend longitudinally through the entire bore 127 of a casing string 142of a barrier. Further, although closure elements 220 are shown in FIG.3A as comprising substantially rectangular cross-sectional shapes, thepresent invention is not so limited. Rather, closure elements 220 maycomprise substantially circular, triangular, rectangular, or shapes asotherwise known in the art.

FIG. 3B shows a perspective view of a sectioned casing section 120interlocked with an adjacent casing section 120. As shown in FIG. 3B,closure elements 220 may each comprise a plurality of closure elementsections 220A and 220B that may abut one another in an end to endrelationship at joints 211, respectively. Each of joints 211 may bewelded via welding apparatus 210 (FIG. 3A), to form an elongated bodyextending generally parallel to longitudinal axis L. For instance, aplurality of closure element sections 220A and 220B may be assembledprior to placement within a bore 127 of each casing section 120 of acasing string 142. Alternatively, assembly of a plurality of closureelements 220 to form an elongated body may occur within the casingstring 142. Further, closure elements 220 may be welded to one anotherin an end to end relationship so as to form an elongated body extendinglongitudinally along the entire bore 127 of a casing string 142.

Further, as shown in FIG. 3C, welds W may be formed along each ofclosure elements 220, affixing each of closure elements 220 to arespective guide feature 123 and a respective male interlockingstructure 124. Welds W may extend substantially continuously along thelongitudinal extent of each of closure elements 220. Thus, at least twocasing strings 142 may be adjoined or affixed to one another through atleast one weld or, as shown in FIG. 3C a plurality of welds W. Further,formation of welds W may substantially seal the interior of bore 127 ofa casing section 120. Also, forming welds W along substantially theentire longitudinal length of a plurality of casing sections 120comprising a casing string 142 may substantially seal the interior bore127 thereof. Such a configuration may be desirable for preventing leaksthrough a subterranean barrier 140 including a plurality of casingstrings 142 so configured.

Alternatively, welding apparatus 210 may comprise a plurality of weldingheads 222, as shown in FIG. 3D. Thus, welds W, as shown in FIG. 3B, maybe formed by a plurality of welding heads 222 each configured forforming a weld within casing section 120 of casing string 142. Weldingheads 222 may be sufficiently positionable within bore 127, individuallyor collectively, for forming each of welds W as shown in FIG. 3B. Thus,in one contemplated configuration, each of welds W shown in FIG. 3B maybe formed substantially simultaneously, by positioning each of theplurality of welding heads 222 proximate a desired region of the sidecross-sectional region of a casing section 120 and operating theplurality of welding heads 222 while moving same longitudinally withinthe bore 127 of casing section 120. Such a configuration may provide arelatively fast and efficient process for forming welds W.

In a further aspect of the present invention, nondestructive inspectionor verification of at least a portion of the at least one weld formedfor adjoining two adjacent casing strings 142 may be performed. Manydifferent types of so-called non-destructive testing (NDT) or evaluationtechniques for inspection or verification of welds are known in the art.For instance, visual (e.g., dye penetrant), ultrasonic, magneticparticle inspection, radiography, (e.g., x-ray or gamma ray), eddycurrent, or combinations thereof may be employed for verification of atleast a portion of at least one weld formed for joining adjacent casingstrings 142 to one another. More specifically, as shown in FIG. 4A, aNDT apparatus 310 for performing NDT of at least one weld formed betweentwo casing strings 142 may be disposed within one of casing strings 142and operated to perform verification of at least one characteristic orquality of the at least one weld formed therebetween. As shown in FIG.4A, NDT apparatus 310 may be positioned within a bore 127 of a casingstring 142 by way of positioning legs 312 and may be configured forinteraction with the welds W formed therein. For instance, NDT apparatus310 may include a dye penetrant application system and a camera or othervisual inspection device for performing dye penetrant and visualinspection of at least one of welds W. Of course, data (e.g., images,radiographic detection, etc.) collected or otherwise sensed by way ofNDT apparatus 310 may be transmitted therefrom and outside of a casingstring through wires, radio signal, or other communication technology asknown in the art.

In another embodiment of a NDT apparatus 310B, as shown in FIG. 4B,since an adjacent casing string 142 may be available for use ininspecting at least one weld formed between two casing strings 142, aNDT apparatus 310B which emits a radiographic signal (e.g., x-rays,gamma rays, etc.) that is transmitted through at least one of welds Wand toward an adjacent casing string 142 may be particularlyadvantageous. As shown in FIG. 4B, a NDT apparatus 310B according to thepresent invention is shown including a radiographic source 304, such asan x-ray tube, positioned within bore 127 of casing section 120 andconfigured for emitting a radiographic signal 311 toward adjacent casingsection 120, as shown in FIG. 4B generally within reference lines 313.Further, NDT apparatus 310B includes a detection device 320 including adetector 322 (e.g., a fluoroscopic screen or film) may be positionedwithin the adjacent casing section 120 for detecting the radiographicsignal 311 emitted from radiographic source 304. Detection device 320may be positioned within bore 127 of casing section 120 by way ofpositioning legs 332 and other positioning members (not shown) forpreventing detector 322 from contacting tubular body 126 of casingsection 120. Of course, the radiographic source 304 and the detectiondevice 320 may be configured for coordinated movement or positioningwith respect to one another while positioned within different casingstrings 142, respectively.

Verifying at least one characteristic or quality of at least a portionof at least one weld formed by welding apparatus 210 may be performed byNDT apparatus following in the direction in which at least one is beingformed, proximate thereto, or, alternatively, a NDT apparatus may beplaced within a bore 127 of a casing string 142 subsequent to completionof a welding process therein. Accordingly, in one example, at least onecharacteristic of at least a portion of at least one weld formed bywelding apparatus 210 may be verified as the welding apparatus 210continues to form the at least one weld. Alternatively, at least aportion of at least one weld may be formed subsequent to the weldingapparatus 210 forming a desired portion or an entire length of at leastone weld.

Upon detection of an anomaly within a portion of a weld, repair thereofmay be performed. Welding apparatus 210 may be configured for repairinga portion of a weld that is indicated as requiring or otherwise may bedesignated for repair. For instance, removal of a portion of the weldvia grinding, cutting, or machining, as well as subsequent additionalwelding, or both may be performed by welding apparatus 210 for repairinga flaw or anomaly that is detected in a weld or a portion of a weld thatmay be selected for repair.

In yet a further aspect of the present invention, subsequent to weldingan interlocking structure of a casing string 142 to form an at leastsubstantially closed or sealed elongated bore 127 extending therein, thefree ends of the casing string 142 may be sealed, as by welding a capthereon, respectively and the interior of the casing string 142 may bepressurized with a gas through a port installed for communicationtherewith. Further, the pressure developed within the interior of thecasing string 142 may be monitored (e.g., via at least one pressuretransducer), for verifying that the interior of the casing string ishermetically sealed. Such a configuration may provide a relativelysimple and robust indication of integrity of a casing string 142 and,overall, of a barrier formed therewith.

It is further contemplated by the present invention that at least aportion of a casing string 142 may be removed from a subterraneanbarrier 140 and repaired or replaced. For instance, welding apparatus210 may be capable of removing a portion of casing section 120 (i.e.,grinding, cutting, or machining so as to form pieces thereof that may beremovable from within a bore of the casing string). Thus, at least aportion of a casing section 120 may be repaired by cutting and removinga selected portion thereof, positioning a replacement or repair elementtherein, and welding the repair element into the existing casing string142 by way of a welding apparatus 210 as described above.

As may be readily appreciated by one of ordinary skill in the art,casing sections 120 may be structured in various, different embodiments.For example, and not by way of limitation, casing sections 120 maycomprise interlocking structures as described in U.S. Pat. No. 6,758,634to Nickelson and U.S. patent application Ser. No. 10/358,633 toNickelson, each of which is assigned to the assignee of the presentinvention and the disclosures of each of which are incorporated in theirentirety by reference herein. Further, casing sections may be structuredfor facilitating forming of at least one weld therebetween or forimproving or simplifying a welding process related to forming at leastone weld therebetween.

More specifically, in one exemplary embodiment, FIGS. 5A and 5B show aside cross-sectional view and an enlarged partial side cross-sectionalview of interlocking structure 130, respectively. More specifically,interlocking structure 130 may comprise a male interlocking structure124 configured as a generally L-shaped outwardly extending feature,relative to the tubular body 126 of casing section 120, disposed withinan associated female interlocking structure 122. It may be noted thatthe at least one female interlocking structure 122 may comprise a recess121 opening into the bore 127 of a casing section 120 and a frangibleprotective element 144 may be provided on the outer radial surface ofits tubular body 126 for preventing contaminants from entering bore 127.For instance, frangible protective element 144 may comprise a plasticsheet material that is wound circumferentially about the casing section120.

According to the present invention, at least one weld may be formed forjoining male interlocking structure 124 to female interlocking structure122. Thus, FIG. 5B shows an enlarged side cross-sectional view ofinterlocking structure 130, including substantially cylindrical,differently sized, substantially circular closure element sections 220Band 220C and welds W. More specifically, two of welds W are formedbetween the male interlocking structure 124 and both closure elementsections 220B and 220C, respectively. Further, two of welds W are formedbetween closure element sections 220B and 220C. Thus, male interlockingstructure 124 may be described as being indirectly affixed or joined tofemale interlocking structure 122 through substantially circular closureelement sections 220B and 220C.

As a further consideration, an interlocking structure of the presentinvention may include at least one sealing element. Further, forming atleast one weld for adjoining respective portions of an interlockingstructure may cause at least partial melting of the at least one sealingelement. Such a configuration may provide increased resistance toleakage through the interlocking structure. For example, FIG. 6 shows anenlarged side cross-sectional view of the interlocking structure 130, asshown in FIG. 3C, but also including elongated sealing elements 240,extending longitudinally along the length of guide features 123, betweenguide features 123 and male interlocking structure 124. Sealing elements240 may comprise a polymer, such as a plastic (e.g., nylon,polyethylene, etc.). Sealing elements 240 may be structured for reducingthe overall (i.e., along the length) amount of clearance between maleinterlocking structure 124 and female interlocking structure 122.However, sealing elements 240 may, under the forces and contact betweenmale interlocking structure 124 and female interlocking structure 122,be configured for abrading, deforming, or otherwise accommodatingassembly thereof. Thus, upon assembly of an entire casing string 142adjacent and interlocked with another casing string 142, some regions ofsealing elements 240 may be deformed or abraded away, while otherregions may be as shown in FIG. 6.

Further, in another aspect of the present invention, forming welds W asshown in FIG. 6 may provide sufficient heat to at least partially meltsealing elements 240. As used herein, “melt” refers to heating amaterial such that a glass transition temperature of the material isexceeded. Thus, sealing elements 240 may be sized, configured, orstructured for at least partially melting in response to forming atleast one weld proximate thereto. Alternatively, an area proximate eachof sealing elements 240 may be heated so as to at least partially melteach of sealing elements 240. For example, heating regions 241 withinbore 127 of tubular body 126 may at least partially melt sealingelements 240. Alternatively, welds W may be heated subsequent toformation thereof for at least partially melting sealing elements 240.Of course, a welding apparatus 210 as described above may be employedfor heating a region of a casing section 120, such as heating regions241. At least partially melting the sealing elements 240 may beadvantageous for providing additional resistance to leakage throughadjacent casing strings 142 of a subterranean barrier 140.

In another exemplary interlocking structure embodiment according to thepresent invention, FIG. 7A shows a partial cross-sectional view of aportion of interlocking structure 130 including two interlocked,adjacent casing sections 120, each casing section 120 including atubular body 126 forming a bore 127, generally as described above withrespect to FIGS. 5A and 5B. Female interlocking structure 122 includesan interior guide feature 128, which forms, in combination with portionsof its associated tubular body 126, a recess 121. Male interlockingstructure 124, as shown in FIG. 7A, is configured as a generallyL-shaped feature, having a leg section thereof extending toward thetubular body 126 of casing section 120. Further, sealing elements 240may be positioned between the male interlocking structure 124 and theopening 137 of female interlocking structure 122.

Turning to FIG. 7B, welds W may be formed upon the end regions of bothL-shaped male interlocking structure 124 as well as interior guidefeature 128, for affixing the L-shaped male interlocking structure 124to the interior guide feature 128 and the L-shaped male interlockingstructure 124 to the tubular body 126 of casing section 120. As shown inFIG. 7B, formation of welds W substantially closes recess 121 and recess129. Once recess 121 and recess 129 are substantially closed, one orboth may be filled with a sealant or filler material. More generally,any space or volume within the female interlocking structure 122 notoccupied with male interlocking structure 124 may be filled with asealant such as grout or bentonite to provide further resistance topermeation.

Optionally, a force 150 may be applied for biasing an end region ofinterior guide feature 128 toward L-shaped male interlocking structure124 during formation of the weld W therebetween. Force 150 may begenerated or applied by way of a welding apparatus 210 (FIG. 3A).Alternatively, if force 150 is of sufficient magnitude, both theL-shaped male interlocking structure 124 and the interior guide feature128 may be biased toward the tubular body 126 of casing section 120.Thus, at least one of the interior guide feature 128 and the L-shapedmale interlocking structure 124 may be fixed by a weld in a biasedposition. Explaining further, biasing or biased refers to displacementfrom an equilibrium position, wherein an equilibrium position may be aposition of a male or female interlocking structure as they are at leastpartially cooperatively engaged with one another but generally free fromexternal forces. Of course, a male and a female interlocking structuremay be biased (e.g., exert or produce forces upon one another) by virtueof at least partially cooperatively engaging one another. Additionally,biasing of a male or female interlocking structure may develop stressestherein in response to such biasing. Thus, at least one of the interiorguide feature 128 and the L-shaped male interlocking structure 124 maybe fixed by a weld in a stressed condition.

Biasing one or both of L-shaped male interlocking structure 124 and theinterior guide feature 128 may be desirable for improving thecharacteristics of at least one of welds W. Also, such a configurationmay reduce the number of welds W that must be formed to substantiallyseal the interlocking structure 130 along its longitudinal extent.Further, reducing the number of welds W formed for substantially sealingan interlocking structure 130 may also simplify the apparatus or methodsfor verification of the integrity of the welds W, which may beadvantageous.

In yet a further exemplary embodiment of an interlocking structure 130according to the present invention, FIG. 8A shows two adjacent,substantially rectangular casing sections 120B. Casing sections 120B areinterlocked to one another via interlocking structure 130 including anunsymmetrical T-shaped male interlocking structure 124, and anassociated female interlocking structure 122, formed, in part, by apartially C-shaped interior guide feature 138. Interior guide feature138 forms, in combination with portions of its associated tubular body136, a recess 121 having an opening 155 formed between interior guidefeature 138 and tubular body 136. As shown in FIG. 8A, the upper end ofmale interlocking structure 124 may be sized and configured to begenerally within opening 155, proximate both the C-shaped interior guidefeature 138 as well as tubular body 136 of the casing section 120.

Turning to FIG. 8B, weld W may be formed upon the end regions of bothT-shaped male interlocking structure 124 as well as the partiallyC-shaped interior guide feature 138, for affixing the T-shaped maleinterlocking structure 124 to the interior guide feature 138 and theT-shaped male interlocking structure 124 to the tubular body 136 ofcasing section 120B. As shown in FIG. 7B, formation of weld W maysubstantially close or seal recess 121. As explained above, once recess121 is substantially closed, it may be filled with a sealant or fillermaterial.

Optionally, force 150, force 151, both or a selected force may beapplied to at least one of partially C-shaped interior guide feature 128and T-shaped male interlocking structure 124 for biasing an end regionof partially C-shaped interior guide feature 128 toward substantiallytubular body 136 of casing section 120B during formation of the weld Wtherebetween. Such biasing may be considered in the design of at leastone of the male interlocking structure 124 and the female interlockingstructure 122. Put another way, at least one of the male interlockingstructure 124 and the female interlocking structure 122 may be designedfor exhibiting a desired magnitude of displacement in response to ananticipated magnitude of force applied thereto in a selected direction.

Forces 150 and 151 may be generated, for instance, by way of weldingapparatus 210 (FIG. 3A). Biasing partially C-shaped male interlockingstructure 124 and the interior guide feature 128 may be desirable forimproving at least one characteristic of weld W. Also, as shown in FIG.8B, such a configuration may require but a single weld W tosubstantially seal the interlocking structure 130 along its longitudinalextent. Of course, forming a single weld W may simplify the apparatus ormethods for verification of the integrity thereof, which may beadvantageous.

In addition, although the present invention is generally described aspertaining to interlocked casing sections or casing strings, the presentinvention is not so limited. Rather, generally, the present inventioncontemplates a plurality of tubular casing strings positioned within asubterranean formation, wherein at least two of the plurality of tubularcasing strings are structured and positioned with respect to one anotherfor forming at least one weld therebetween. Thus, the present inventioncontemplates that two adjacent casing sections (of two adjacent casingstrings) may include welding structures and may be positioned so thatthose welding structures abut or lie proximate one another for formingat least one weld therebetween, without limitation.

As may be appreciated from the above description, the present inventioncontemplates many different configurations and possible configurationsand structures pertaining to interlocking structures of casing strings.For instance, a substantially sealed recess may be formed subsequent tosubstantially sealing an interlocking structure via at least one weld.More specifically, FIG. 9 shows the interlock structure shown in FIG.5B, but including a channel feature 160. Channel feature 160 may bewelded, subsequent to welds W being formed, to tubular body 126 ofcasing section 120 via welds W2 by way of a welding apparatus asdescribed above to form a substantially closed recess 121. As shown inFIG. 9, substantially closed recess 121 may be filled with a fillermaterial 170.

Generally, as mentioned hereinabove, subsequent to welding adjacentcasing sections 120 of casing strings 142 (FIG. 1A) as well asinterlocking structures of adjacent casing sections 120, at least aportion of casing strings 142 or casing sections 120 comprising same maybe preferably substantially filled (within their bores 127, recesses121, or both) with a filler material (not shown) such as grout, wax,rubbers, tar, polymeric sealants, thermoplastic polymers, thermosetpolymers, cement, concrete, bentonite-based materials, modified cement,polysiloxane, acrylic polymers, or the like. Some of these fillermaterials, such as the thermoplastic polymers, waxes, and tar may alsopossess a degree of “self-healing” ability being able to slowly flow ormove to recreate a breached seal without further intervention.

For instance, filler material may comprise a tar which is flowed withincasing strings 142 (FIG. 1) and interlocking structures thereof andsubsequently solidifies to form a substantially leak-tight subterraneanbarrier 140 (FIG. 1). More generally, filler material comprising aliquid, slurry, granular material, or other flowable state (i.e., freelymovable) may be disposed within the interlocking structures and,optionally, may be subsequently solidified to form a substantiallycontinuous leak-tight subterranean barrier 140. Also, as known in theart, filler material disposed within bores 127, recesses 121, or both ofcasing sections 120 may produce a subterranean barrier 140 that isrelatively chemically stable, even when exposed to solutions saturatedwith calcite, gypsum, or other reactive solutions.

Such a barrier configuration may be desirable, because a subterraneanbarrier 140 including interlocked casing strings 142 (FIG. 1) as well asincluding filler material (not shown) may exhibit a high degree ofstructural continuity and strength. Additionally, such a subterraneanbarrier 140 may demonstrate a relatively low hydraulic conductivity,which means that subterranean barrier 140 may be substantiallyimpermeable to leachate or gas emitted from buried waste 133 (FIG. 1).Subterranean barrier 140 may also be thermally stable and may retain itsstructural integrity and hydraulic conductivity under a wide variety ofphysical and thermal conditions including ground shifting, andrelatively large temperature gradients. Also, subterranean barrier 140may be configured for use in environments that experience cyclicalfreeze and thaw temperature conditions and in environments whereprecipitation may cause the presence of groundwater flow.

However, even a barrier that is filled with a material may eventuallydevelop a leak due to repeated thermal stresses, displacement orshifting of the casing strings, or other environmental influences.Conventionally, a specialized repair apparatus, such as aremote-controlled robot that fits inside a casing string 142, may bemoved to the location of a detected void for removal thereof. Further, adrill or other machining or material removal tool may be employed viathe remote-controlled robot to remove a sufficient portion of the fillermaterial such that the void is removed. Then, the void may be filledwith additional barrier filler. Such a process may be analogized to theprocess of dental filling. Furthermore, such a process may be relativelytime consuming and difficult to perform. Of course, filler materialwithin the casing string 142 would need to be removed, if present toallow for a remote-controlled robot to travel therein. Alternatively,only the interlocking structures of a barrier may be filled with fillermaterial.

Accordingly, in another aspect of the present invention, a heatingapparatus, such as a welding apparatus as described above may beemployed to selectively heat at least a portion of at least one casingstring of a barrier, as described briefly hereinabove. For instance,selectively heating at least a portion of at least one casing string ofa barrier may be advantageous for repairing cracks in filling material.As mentioned above, interlocking structures of adjacent casing sectionsmay be preferably substantially filled with a filler material such asgrout, wax, tar, cement, concrete, bentonite-based materials, modifiedcement, polysiloxane, acrylic polymers, or the like. More particularly,FIG. 10 shows three adjacent casing sections 120 interlocked with oneanother. Each of casing sections 120 is substantially identical and eachincludes three female interlocking structures 122 and one maleinterlocking structure 124. As shown in FIG. 10, filler material 170 isdisposed within recess 121 of interlocking structure 130 and includedflaw 199. Interlocking structure 130 may be structured and formedgenerally as described and shown in FIG. 9. Further, selectively heatingthe channel feature 160 may mend or repair flaw 199. As shown in FIG.10, heat Q is applied generally toward the channel feature 160.

Heat Q may be generated by a welding apparatus or, alternatively, aheating apparatus. Heat may be generated as known in the art, forinstance, heat Q may be generated by a laser beam, induction heating,electrical current, a torch or flame, or combinations thereof.Selectively heating a desired longitudinal region of a casing section120 may be advantageous for efficiently repairing a portion of asubterranean barrier 140. Alternatively, selectively heating at least aportion of a casing string of a barrier may be desirable for expandingor curing filler material disposed within a bore of a casing section ora recess of an interlocking structure. Of course, heating may be appliedfrom one casing string 142 for heating an adjacent casing string.Further, heating at least a portion of a casing string may facilitatefilling thereof with filler material. For instance, if the bore orrecess is heated prior to or during filling with wax or tar, such mayflow more easily therein.

In a further aspect of the present invention, the present inventioncontemplates that an adhesive may be deposited between a femaleinterlocking structure of one casing string and a male interlockingstructure of another adjacent casing string for forming an adhesive bondtherebetween. Such a configuration may be analogized to theabove-description regarding forming at least one weld, except that atleast one adhesive region may be formed. Thus, the present inventioncontemplates that any of the above-described embodiments may include anadhesive region formed in the position and configuration as is shown anddescribed with respect to welds W but in place thereof. Further, thepresent invention contemplates that welds, adhesive regions, orcombinations thereof may be employed for affixing or bonding one casingstring to an adjacent casing string, without limitation.

For example, an adhesive affixation process according to the presentinvention will be described with reference to FIGS. 11A-11B.Particularly, FIG. 11A shows a partial side cross-sectional view of twocasing sections 120 of respective, adjacent, interlocked casing strings142, as shown in FIG. 2, including an adhesive affixation apparatus 310positioned within bore 127 of one casing section 120 by positioning legs312. Positioning legs 312 may include one or more wheels and may bebiased by way of a biasing element (not shown) configured forpositioning adhesive affixation apparatus 310 within a bore of asubstantially tubular structure, such as the (substantially circular)bore 127 of casing section 120. Also, adhesive affixation apparatus 310may be movable along the length of a casing string 142, within a bore127 of one of the plurality of casing sections 120 comprising same. Ofcourse, adhesive affixation apparatus 310 may be configured fordepositing an adhesive between of casing strings 142. In one example, anadhesive may be deposited as a flowable material that subsequently atleast partially cures or hardens. Additionally, adhesive affixationapparatus 310 may include apparatus for hardening or curing an adhesive(e.g., light or heat). However, the present invention contemplates thatan adhesive deposited by adhesive affixation apparatus 310 may compriseany adhesive as known in the art, without limitation. For example, anadhesive deposited by adhesive affixation apparatus 310 may comprise anepoxy, an acrylic, an acrylate, a phenolic, a formaldehyde, apolyurethane, a polyester, a silicone, a vinyl, a vinyl ester, athermosetting plastic, combinations thereof, or other adhesiveformulations as known in the art.

In further detail, least one adhesive depositing head 322 may be affixedto adhesive affixation apparatus 310 and configured for movement withina bore 127 of casing section 120, so as to be selectively positionablefor depositing an adhesive upon a desired portion of an interior of acasing section 120. Thus, adhesive joints B, as shown in FIG. 11A, maybe formed by an adhesive affixation apparatus 310 including a singleadhesive depositing head 322, as shown in FIG. 11A, configured fordepositing adhesive within casing section 120 of casing string 142.Alternatively, adhesive affixation apparatus 310 may include a pluralityof adhesive depositing heads (i.e., a plurality of adhesive depositingheads 322). Adhesive depositing head 222 may be at least sufficientlypositionable within bore 127 for forming each of adhesive joints B, asshown in FIG. 11A. In one contemplated configuration, each of adhesivejoints B shown in FIG. 11A may be formed sequentially, by positioningadhesive depositing head 322 proximate a desired region of the sidecross-sectional region of a casing section 120 and operating adhesivedepositing head 322 while moving adhesive depositing head 322longitudinally within the bore 127 of casing section 120. For example,adhesive depositing head 322 may comprise a nozzle for supplyingadhesive toward a region desired to be adhesively bonded.

As explained above with respect to welding, it may be advantageous toemploy closure elements for closing gaps between a male interlockingstructure and a female interlocking structure. For instance, in oneembodiment, as shown in FIG. 11A, closure elements 220 may be placedadjacent guide features 123 and male interlocking structure 124,respectively. Closure elements 220 may be configured for substantiallyor completely closing, collectively and upon welding of each closureelement 220 to a respective guide feature 123 and a respective portionof male interlocking structure 124, gaps g formed between the femaleinterlocking structure 122 and the male interlocking structure 124. Putanother way, since clearance between male interlocking structure 124 andguide features 123 may be desirable for assembling adjacent casingstrings 142 to one another, a closure element 220 may be configured formatingly engaging both a guide feature 123 and a male interlockingstructure 124 so as to substantially or completely close the clearanceor gap upon welding of the closure element 220 to both the maleinterlocking structure 124 and a guide feature 123.

Of course, adhesive depositing apparatus 310 may be configured forpositioning closure elements 220 in a desired position, as shown in FIG.11A. In one embodiment, closure elements 220 may comprise a so-called“bar stock,” comprising an elongated body having a substantiallyconstant cross section and comprising a material such as, for instance,steel, aluminum, a polymer, or another material compatible foradhesively affixing male interlocking structure 124 and guide feature123, and may exhibit a cross-sectional shape that is suitable formatingly engaging, if properly positioned, both a guide feature 123 andthe male interlocking structure 124. Alternatively, closure elements 220may comprise a polymer such as PVC, HDPE, polypropylene, PVDF, or thelike, without limitation.

Thus, generally, according to the present invention, at least one weldmay be formed for joining a male interlocking structure to a femaleinterlocking structure. In a further example, as shown in FIG. 11B,which shows an interlocking structure as shown in FIG. 5B, adhesivejoints B may be formed along and around each of closure elements 220,affixing each of closure elements 220 to a respective guide feature 123and a respective male interlocking structure 124. Adhesive joints B mayextend substantially continuously along the longitudinal extent of eachof closure elements 220. It may be appreciated that adhesive joints Bare shown as substantially surrounding closure elements 220, which maybe effected by applying adhesive in a region desired to be adhesivelyaffixed and then positioning closure elements 220 thereinto.

More specifically, FIG. 11B shows an enlarged side cross-sectional viewof interlocking structure 130, including substantially cylindrical,differently sized, substantially circular closure element sections 220Band 220C and adhesive joints B. More specifically, two of adhesivejoints B are formed between the male interlocking structure 124 and bothclosure element sections 220B and 220C, respectively. Further, two ofadhesive joints B are formed between closure element sections 220B and220C. Thus, male interlocking structure 124 may be described as beingindirectly affixed or joined to female interlocking structure 122through substantially circular closure element sections 220B and 220C.

Thus, in general, at least two casing strings 142 may be adjoined oraffixed to one another through at least one adhesive joint B.Particularly, as mentioned above, an adhesive joint B may beinterchangeable, for purposes of disclosure, with a weld W or W2 asshown in any of the above-described embodiments. Further, adhesive jointB may be formed according to any of the above-described methods asdisclosed above with respect to a weld W or W2. Optionally, at least oneweld and at least one adhesive joint may be used in combination with oneanother for joining at least two casing strings to one another.

Also, as shown in FIGS. 11A and 11B, at least two casing strings 142 maybe adjoined or affixed to one another through a plurality of adhesivejoints B. Further, formation of adhesive joints B may substantially sealthe interior of bore 127 of a casing section 120. Also, forming adhesivejoints B along substantially the entire longitudinal length of aplurality of casing sections 120 comprising a casing string 142 maysubstantially seal the interior bore 127 thereof. Such a configurationmay be desirable for preventing leaks through a subterranean barrier 140including a plurality of casing strings 142 so configured.

While the present invention has been described herein with respect tocertain exemplary embodiments, those of ordinary skill in the art willrecognize and appreciate that it is not so limited. Rather, manyadditions, deletions and modifications to the exemplary embodiments maybe made without departing from the scope of the invention as hereinafterclaimed. In addition, features from one embodiment may be combined withfeatures of another embodiment while still being encompassed within thescope of the invention as contemplated by the inventors. Therefore, theinvention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by thefollowing appended claims.

1. A method of forming a subterranean baffler adjacent a selected region of a subterranean formation, comprising: placing a plurality of casing strings within a subterranean formation, each casing string of the plurality of casing strings comprising a bore extending longitudinally through at least a portion thereof, each of the plurality of casing strings being laterally adjacent to at least one other casing string of the plurality of casing strings; interlocking each casing string of the plurality of casing strings to at least one adjacent casing string through an interlocking structure extending between at least one casing string of the plurality of casing strings and at least another adjacent casing string of the plurality of casing strings; joining at least two laterally adjacent casing strings of the plurality of casing strings to one another by forming at least one weld substantially longitudinally along the interlocking structure formed between two adjacent casing strings; and disposing baffler filler material at least partially within the interlocking structure.
 2. The method of claim 1, wherein forming the at least one weld comprises a weld selected from the group consisting of gas welding, arc welding, gas-shielded arc welding, oxyfuel welding, laser welding, induction welding, electron beam welding, chemical welding, ultrasonic welding, and resistance welding.
 3. The method of claim 1, wherein interlocking the at least two casing strings comprises positioning a male interlocking structure at least partially within a female interlocking structure.
 4. The method of claim 3, wherein joining the at least two laterally adjacent casing strings of the plurality of casing strings to one another by forming the at least one weld comprises forming at least one weld between one of the at least two laterally adjacent casing strings and one of the male interlocking structure and the female interlocking structure.
 5. The method of claim 3, further comprising displacing at least one of the male interlocking structure and the female interlocking structure in relation to an equilibrium condition thereof during forming the at least one weld.
 6. The method of claim 1, further comprising substantially filling at least one interlocking structure extending between two laterally adjacent casing strings of the plurality with barrier filler material.
 7. The method of claim 1, wherein joining the at least two laterally adjacent casing strings of the plurality of casing strings to one another by forming the at least one weld comprises forming a plurality of welds.
 8. The method of claim 1, wherein joining at least two laterally adjacent casing strings of the plurality of casing strings to one another by forming at least one weld comprises positioning a welding apparatus within one of the at least two laterally adjacent casing strings of the plurality of casing strings and operating the welding apparatus so as to form the at least one weld.
 9. The method of claim 8, further comprising moving the welding apparatus within the one of the at least two laterally adjacent casing strings of the plurality of casing strings while operating the welding apparatus so as to form the at least one weld. 